(1) Field of the Invention
This invention relates to a method for a circular machining of eccentric shaft portions, particularly crankpins of crankshafts, comprising an externally cutting, rotating or oscillating tool, such as a grinding wheel, a tool of a superfinishing device, or an end mill, which tool is longitudinally positioned to engage the shaft portion and machines the same as an angular feed movement relative to the workpiece is imparted to the tool.
(2) Description of the Prior Art
To permit a higher surface finish to be obtained and smaller dimensional tolerances to be adhered to, it is often necessary to machine workpieces in a plurality of operations. In most cases the workpieces are milled or turned and then finished by grinding or superfinishing. These finishing operations are performed by externally cutting tools, which rotate or oscillate. So far, to use of such driven tools for machining eccentric shaft portions, such as the crankpins of a crankshaft, has been time-consuming and complicated and has required expensive machine tools because an angular feed movement is to be imparted to the workpiece as it is machined and for this purpose the workpiece must be rotated about the axis of the eccentric portion which is to be machined. For this purpose the workpiece must be eccentrically gripped and its gripping arrangement must be changed when a different portion is to be machined. Besides, expensive means are required for driving the workpiece and the rotation of the workpiece involves a rotary unbalance, which adversely affects the machining conditions.